基于改进LBM的气液自发渗吸过程中动态润湿效应模拟

微通道内气液自发渗吸是广泛发生在自然界及诸多工业领域的物理现象,而动态接触角是影响整个渗吸过程的关键因素.针对该问题,本文使用改进的伪势多相流格子玻尔兹曼方法 (LBM),直接捕捉微通道内气液自发渗吸过程中的实时接触角,并分析接触角的动态变化特性及其对渗吸长度的影响.首先,本文在原始的伪势多相流LBM的基础上耦合Peng-Robinson (PR)状态方程,改进流体-流体作用力以及流-固作用力格式,并采用精确差分方法将外力添加至LBM框架中.然后,通过校准模型的热力学一致性,模拟测试界面张力,静态平衡接触角等界面现象验证了模型的准确性.最后,基于建立的模拟方法,在水平方向上模拟微通道内气液自发渗吸过程.结果表明:渗吸过程中的接触角呈现动态变化特征,在渗吸初期,因受到惯性力的影响存在较大波动;随着渗吸距离的增大,其逐渐减小并趋近于静态平衡接触角.渗吸过程中的接触角与微通道尺寸及静态接触角有关,随着微通道宽度增大,实时的动态接触角与静态接触角相差大;随着静态接触角增大,实时的动态接触角与静态接触角的相差增大.此外,忽略动态接触角的Lucas-Washburn (LW)方程所预测的弯液面位置...

SIMULATION OF DYNAMIC WETTING EFFECT DURING GAS-LIQUID SPONTANEOUS IMBIBITION BASED ON MODIFIED LBM

Gas-liquid spontaneous imbibition in microchannels is a widely occurring physical phenomenon in nature and many industrial fields. The dynamic contact angle is the key factor affecting the whole gas-liquid imbibition process. In this work, we use a modified pseudopotential multiphase flow lattice Boltzmann method (LBM) to capture the real-time contact angle during gas-liquid spontaneous imbibition in microchannels and analyze the dynamic characteristics of the contact angle and its effects on the imbibition length. Firstly, we coupled the Peng-Robinson (PR) equation of state to the original pseudopotential multiphase flow LBM, improved the fluid-fluid interaction force and fluid-solid interaction force formats, and added the external forces to the LBM framework by using the exact difference method. Then, the accuracy of the model was verified by calibrating the thermodynamic consistency of the model and simulating interfacial phenomena such as interfacial tension and static equilibrium contact angles. Finally, based on the established simulation method, the spontaneous gas-liquid percolation process in the microchannel is simulated in the horizontal direction. The results show that the contact angle in the imbibition process is dynamic and varies greatly in the early stage of imbibition due to the inertia force. With the further increase of the imbibition distance, it gradually decreases and tends to the static equilibrium contact angle. The contact angle in the imbibition process is related to the microchannel size and the static contact angle. As the width of the microchannel increases, the difference between the dynamic contact angle and the static contact angle in real-time increases; as the static contact angle increases, the difference between the dynamic contact angle and the static contact angle in real-time increases. In addition, the Lucas-Washburn (LW) equation, which ignores the dynamic contact angle, predicts the position of the meniscus is different from the simulated results. The real-time dynamic contact angle data obtained from the simulations can be directly applied to correct the LW equation, and the corrected LW equation predicts the position of the meniscus in general agreement with the simulated results.